Conventional cushions, e.g., serving as a pillow case or cover, are produced in which two superimposed cover parts are sewn together along their edges on three sides and then the pillow case or cover is turned inside out so that the seam edges are then located inside of the pillow case or cover. The side which was left open is closed by a zipper or the like. This does not provide a gas impermeable closure.
Conventional gas impermeable closures are produced in that two layers of a plastic film, e.g., two PVC-layers, are welded together on their outsides. Furthermore, dirt may collect in them, which is undesirable from a hygienic point of view.
A cushion of the invention is suitable for a positioning aid for positioning and holding stationary parts of a patient's body, in particular relative to a medical apparatus or a device for medical treatment or diagnosis, or a part thereof, e.g., a measuring coil of a magnetic resonance imaging tomograph.
Nowadays nuclear magnetic resonance tomography is being increasingly used in the framework of modern technology for medical diagnosis. For examining extremities, i.e. arms and legs, measuring coils in the shape of ring coils, surface flex coils and the like are slid over, e.g., an arm or a leg or placed on another body part to be examined, e.g. the torso, shoulder or neck. To obtain good investigation results, the body part to be checked should not perform any movements relative to the measuring coil during the measurement. This is very difficult because usually the scanning or measuring time of a nuclear magnetic resonance tomograph takes 30 to 45 minutes. During this long time the body part to be measured must be kept jitter-free to ensure a sufficiently clear insight into the body part to be examined for diagnosis.
At present, legs and arms are usually scanned by sliding a ring-shaped measuring coil or a surface coil of the nuclear magnetic resonance tomograph over the leg or arm to be scanned up to the area to be checked. Then the patient puts this body part, together with the measuring coil, onto a table or an adequate support. If another body part, e.g. part of the torso, is to be measured by applying a measuring coil, the person to be examined is placed onto a patient table. In many cases this depositing of the body part to be investigated together with the measuring coil does not result in the desired prevention of movements of the body part to be examined relative to the measuring coil during the long measuring time. As a consequence, the measuring results become less reliable.
As far as examinations of arms and legs are concerned, this problem is addressed by German Utility Model Application G 94 07 862.9, which suggests to mount a stand to the patient table on which the patient lies during a measuring process with a nuclear magnetic resonance tomograph. Said stand comprises a foot which is mounted next to the surface on which the patient lies such that it can be displaced relative to the patient table and an arm which is held angularly movable by a ball joint on one end of the stand's foot and which is provided with a holder for taking up a measuring coil on the other end.
Such a stand has proven useful because the body part to be examined can be kept effectively stationary even for an extended time.
However, such a stand is relatively expensive and requires the installation of various measuring coils on the measuring coil holder, depending on the body part to be examined. It may even be an obstacle when other body parts, e.g. torso parts, are to be measured. Furthermore, it may be difficult for some patients if their arm or leg is held only by a relatively short measuring coil compared to the length of the arm or leg for a relatively long time.
If, for instance, the torso area of a patient is placed on a patient table on which it is difficult to lie completely still, there is the danger of undesirable movements of the person.
These problems can be overcome by an inflatable cushion having a special valve, as described below.